FIG. 1 is the schematic diagram of the frame structure of the Long Term Evolution (LTE) system. In the LTE system, a 10 ms radio frame is divided into two half frames, each of which is partitioned into 10 time slots with a length of 0.5 ms, 2 time slots form one subframe with a length of 1 ms, and one half frame comprises 5 subframes.
For normal cyclic prefixes with lengths of 5.21 μs and 4.69 μs, one time slot comprises 7 uplink/downlink symbols a with length of 66.7 μs, wherein the cyclic prefix (CP) of the first symbol has a length of 5.21 μs, and the CP of the other 6 symbols have a length of 4.69 μs; for the extended CP with a length of 16.67 μs, one time slot comprises 6 uplink/downlink symbols.
A Cell ID can be classified into ID1 and ID2, wherein ID1 denotes the sequence number of a cell group, ID1={0,1, . . . ,166,167}, ID2 denotes the sequence number of the cell in the cell group, ID2={0, 1, 2}.
In the Orthogonal Frequency Division Multiplexing (OFDM) system, resource can be presented in two dimensions including time and frequency.
FIG. 2 is a schematic diagram showing the downlink pilot location when the CP is a normal CP, wherein 1 denotes the sequence number of an OFDM symbol, T1 denotes the pilot of the first antenna, T2 denotes the pilot of the second antenna, T3 denotes the pilot of the third antenna, T4 denotes the pilot of the fourth antenna.
The frequency domain locations of the downlink pilots are as follows,
The initial location of the pilot on the first antenna is the kth sub-carrier (k=0, 1, 2, 3, 4, 5), the distance between neighboring pilots is 6 sub-carriers, and the pilots are arranged in sequence till the last available sub-carrier of the system; The distance between the initial location of the pilot on the second antenna and the initial location of the pilot on the first antenna are 3, that is to say, the initial location of the pilot on the second antenna is (k+3)th sub-carrier, the distance between the neighboring pilots is also 6 sub-carriers, the pilots are arranged in sequence till the last available sub-carrier of the system;
The pilots on the third antenna have the same pilot frequency domain locations as those of the first antenna, the pilots on the fourth antenna have the same pilot frequency domain locations as those of the second antenna;
The time domain locations of the downlink pilots are as follows,
The pilots of the first antenna and the pilots of the second antenna are transmitted at the first OFDM symbol and the third last OFDM symbol in each time slot of downlink sub-frames, and the pilots of the third antenna and the pilots of the fourth antenna are transmitted at the second OFDM symbol in each time slot of downlink sub-frames, which are shown in FIG. 2.
As described above, the pilot initial location, k, on the first antenna has no relationship with the cell ID, there is no mapping relationship therebetween, thus during the implementation of the system, the pilot location can not be determined, which results in the system can not perform various functions.